If you want to look further back, you can also see what queries were hot on a particular day. On Wednesday, May 16th, [melinda doolittle], [halo 3 beta], and [ge dishwasher recall] were on the Hot Trends list. If you don't know why, maybe you'll learn something.
Hot Trends aren't the search terms people look for most often -- those are pretty predictable, like [weather] or [games] or perhaps [myspace]. Yes, [sex] too. Instead, the Hot Trends algorithm analyzes millions of searches to find those that are deviating the most relative to their past traffic. And the outcome is the Hot Trends list.
Google claims it will effectively filter 'inappropriate language' and 'pornography’ from the list – terms that otherwise would probably become a constant on the list.